Frequently Asked Questions
Q. How often should I seal my driveway or parking
lot?
A. A properly constructed asphalt pavement should not need sealing
for at least 3-4 years and even longer depending on the owners
preferences (appearance, construction quality, etc.). Some asphalt
contractors recommend applying a sealer immediately after initial
construction. This would only be necessary if the driveway or parking
lot pavement was improperly placed with poor compaction or other
problems. The purpose of a sealer is to apply some fresh liquid
asphalt to the pavement surface after a number of years when the
surface becomes weathered (turns gray)suffers stone loss or starts
to develop small cracks due to the natural aging process from seasonal
temperature changes, sunlight and oxidation. Owners should inspect
the asphalt surface several times a year (spring and fall) and
consider sealing the pavement when these types of distresses become
apparent. Pavements that have deteriorated more significantly with
larger cracks can have sand added to the sealer at a rate of 2-5
lbs. per gallon to provide additional benefit.
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Q. What is hot mix asphalt?
A. Hot mix asphalt (HMA) is the paving material of choice for
numerous applications in today’s modern world. It is used
to construct heavy duty pavements on interstate highways, airport
runways, racetracks, and for loading/unloading areas at port facilities.
It also serves other purposes such as liners for landfills, drinking
water reservoirs, fish hatcheries and other impoundments. HMA is
universally used as the paving material for parking lots and driveways
and it can also be found serving as a smooth, easy to maintain
surface for playgrounds, tennis courts, hiking/bike trails, and
golf course paths. HMA consists of a mixture of stone (about 95%)
and a glue-like liquid asphalt binder (about 5%) which holds the
stones together in a tough matrix that resists the stresses induced
by traffic and other loadings while providing a smooth, quiet ride
to the traveling public. By varying the size and shape of the stones
and the type and amount of liquid asphalt used, HMA is a unique
product that can be produced to provide the multitude of uses described
above in a safe and cost-effective manner.
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Q. What are the environmental benefits of using hot mix asphalt
as your paving material?
A. One of the important facts about HMA is that it is 100% recyclable
and can be used over and over again. In Virginia, most asphalt
mixes specified for use on roadways allow up to 20% of the material
to be recycled HMA. HMA used as a base material can have over 25%
recycled asphalt pavement (RAP). The use of RAP in HMA provides
a number of benefits:
- It reduces the amount of virgin material used in the mix, thereby
preserving natural resources (stone and liquid asphalt).
- Since it is 100% recyclable it does not need landfill space
for disposal.
- Recycling HMA results in substantial savings to taxpayers (for
road work) and other users.
Another benefit of HMA is that it can provide the lowest levels
of traffic and tire noise. This can be extremely cost effective
in urban areas where the use of sound walls may otherwise be necessary.
Asphalt has been shown in studies to be environmentally benign
as evidenced by its use as a liner for drinking water reservoirs
and fish hatcheries.
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Q. What does the term “Perpetual Pavement” mean?
A. Design engineers looking for value in choosing a pavement type
for heavy duty (thicker) applications should review information
now available on roads paved with HMA that can last indefinitely.
These pavements, called
“perpetual pavements”, having at least 8 inches of
HMA thickness placed along with good construction practices and
proper drainage virtually never need reconstruction. Once in place,
only the surface layers are subject to damage over time and can
be milled off and replaced with the renewed surface providing a
smooth, undamaged pavement for many years. There is no need for
replacement or repair of the lower layers in the pavement structure.
This results in huge cost savings over the long haul for owners
and results in minimal traffic disruptions that would otherwise
result from reconstruction activities.
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Q. What is the most common problem that causes poor quality driveway
pavements?
A. Asphalt mix must be delivered to the jobsite while it is still
very hot, typically at least 250º F. Most driveway paving
contractors do not produce their own mix and buy HMA from larger
highway contractors that have asphalt plants. As a result, mix
can be picked up at an asphalt plant that may not be close to the
driveway’s location. The contractor may also let the truck
loaded with HMA sit around for a period of time while the driveway
area is being prepared for the asphalt placement. This can result
in an unacceptable drop in mix temperature for proper placement
and compaction. A poorly constructed driveway is often the end
result of the mix being placed after it has gotten too cool. One
way to help avoid this problem is to have a minimum mix temperature
at time of placement be part of the contractual agreement with
the contractor.
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Q. Why do construction zones that involve paving with Portland
Cement take so long to be taken down as compared to hot mix asphalt
paving?
A. Concrete pavement construction is a difficult and time consuming
process. Although the concrete industry purports to be able to
quickly place concrete with state of the art pavers and cure it
rapidly with new mix additives, the fact remains that it is much
more time consuming than paving with HMA. Continuously reinforced
concrete pavements require the careful placement of steel within
the slab matrix area and jointed pavements require cutting expansion
joints. These and other issues result in far more time spent by
contractors in the construction zone. HMA placement, on the other
hand, causes few traffic disruptions with paving equipment in and
out of the construction zone in a very short period of time. With
today’s heavy traffic problems, getting the work done quickly
and efficiently while still providing high quality pavements is
of great benefit to owners and the traveling public.
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Q. What can be done to prevent rutting at high stress intersections
(bus lanes, industrial traffic, etc.?
A. Some urban intersections with heavy pavement loadings from
trucks and buses that slow down, stop, start and turn in a relatively
small area at stop signs and traffic lights are very prone to rutting,
pushing and shoving of the mix if the pavement structure and mix
type are not suitable for the stresses being applied. Existing
intersections that repeatedly rut after a short time following
repairs often need to have a “forensic” examination
done to determine the cause of the pavement failure. This involves
cutting a slice out of the problem area pavement (down to the subgrade)
toallow a visual analysis of the failed area.
A determination can
then be made as to whether the pavement deformation goes all the
way through the asphalt and base down to the subgrade or whether
only the surface layer is affected. If the problem is limited to
the surface layer, it is indicative that the mix type or design
is not adequate for the loadings being applied. The remedy would
then be to replace the surface layer with a tougher mix that has
a VDOT specified “D” or “E” designation.
Conversely, if the deformation penetrates through the entire pavement
structure, the repairs must go all the way to subgrade with adequate
structure and mix type being provided. Any observed drainage or
water related problems should also be corrected at that time. A
properly designed and constructed asphalt pavement will not rut,
push or shove even in the most highly stressed intersections
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Q. What is the difference between coal tar and asphalt emulsions
used for sealers? Which should I use?
A. Asphalt emulsions used to seal pavements are typically asphalt
based. Coal tar, a derivative of the coal processing industry can
also be used although asphalt emulsions are most commonly used.
Coal tar based sealers can be somewhat more effective in areas
where lighter fraction petroleum products may drip onto the surface
of the HMA. An example of this would be where poorly maintained
cars or equipment with oil leaks regularly drip their liquids onto
the pavement in the same areas. Coal tar is more affective in repelling
these drippings and preventing softening of the asphalt pavement.
Typical application rates for sealers is about 0.05-0.1 gals./sq.yard.
Latex modifiers and sand can also be added to enhance the sealer’s
effectiveness and allow a thicker application rate. Concentrated
sealing product labels will usually specify the amount of dilution
with water necessary for different applications.
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Q. How can I find out whether a driveway contractor will do a
good job before I sign a contract?
A. There are a large number of driveway paving companies available
to choose from in most areas of Virginia. Picking one that does
good work can sometimes be a challenge. We get numerous complaints
at the association offices about shoddy work done by contractors
in placing asphalt driveways. Since most if not all of these companies
are not members of the Virginia Asphalt Association, we have little
influence on the quality of their work. The best approach to take
to line up a good driveway paving contractor is to check on their
record of complaints at the Better Business Bureau or Consumer
Affairs Office. Poor driveway paving companies will usually leave
a trail of evidence at these watchdog agencies. You should also
investigate similar work performed recently by the contractor if
possible.You can also contact one of our member asphalt producers
from your area (LINK To Member List) and get some
company names of reputable driveway paving contractors.
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Q. What is Stone Mastic Asphalt (SMA)?
A. Stone Mastic Asphalt (SMA) is a relatively new (to Virginia
and the U.S.) asphalt mix that is proving to be a superior paving
material for high traffic roadways such as interstates and primaries.
The mix contains a high percentage of coarser aggregate that is
more cubical in shape and has a higher percentage of liquid asphalt
binder. It provides a strong stone skeleton with good stone on
stone contact to increase stability. Mineral filler and fibers
are added to create a stiff mortar that when combined with the
liquid asphalt helps lock the aggregates together. The mix was
first developed in Europe and has been proven to provide a very
tough and stable pavement that is virtually rut-proof and lasts
much longer than conventional asphalt mixes. The first SMA placed
in Virginia was on I-95 between Washington, D.C. and Richmond in
1993. Since then, the use of SMA on interstates and primary roads
has steadily increased with about 360,000 tons scheduled to be
put down this year. The mix is especially well suited as an overlay
over PCC pavements that are in poor condition. Additional advantages
of SMA from its “grainy”surface texture include a quieter
ride and reduced rainfall induced water over-spray that improves
windshield visibility for the traveling public. The mix is about
20-30% more expensive than conventional asphalt mixes but its long
life, lower maintenance costs and other advantages make it a worthwhile
investment for Virginia Roadways.
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Q. How can I become a member of the Virginia Asphalt Association?
A. The primary group of private companies that comprise the membership
of the Virginia Asphalt Association are asphalt producers. These
companies have the asphalt plants that make the HMA products used
by customers and they also provide paving services for the DOTs,
local and federal government, commercial and other users of HMA.
Over 95% of the HMA placed in Virginia are produced by the VAA’s
asphalt contractor member companies. Other transportation related
company categories that benefit from membership in the VAA include:
- Asphalt Suppliers
- Aggregate Suppliers
- Associate Contractors (milling and placement)
- Specialty Binders and Haulers
- Equipment Companies
- Additives and Paving Services
- Testing Firms and Testing Equipment
- Petroleum Distributors
- Finance, Bonding, Insurance and Legal
- Architects, Engineers and Consultants
All of these companies are involved in activities that provide
services and products that enhance the ability of the asphalt paving
industry to provide safe and economical benefits to the citizens
of Virginia.
Companies interested in becoming a part of the growing membership
of the Virginia Asphalt Association should fill out an application
and submit it to the association office (Link
to Application Form).
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Q. What are the advantages of being able to “mill” out
and replace an asphalt surface layer?
A. The use of milling machines to remove worn out asphalt surfaces
that have completed their service life allows for a very cost-effective
way to restore a roadway surface to a “like new” condition.
The so-called mill-and-fill approach to pavement repairs dramatically
reduces the amount of time a roadway needs to be tied up as a work
zone with all of the related traffic delays and safety concerns.
Milling machines grind out the worn out asphalt then transfer the
material to a haul truck for delivery back to the asphalt plant
for recycling into new mixes. Much of the grade and slope is restored
as part of this process. Meanwhile, immediately behind the milling
machine, pavers can replace the removed material with fresh mix
and have it compacted and turned back over to traffic in a very
short period of time. Another advantage in addition to the short
construction time, restoration of grade and slope and ability to
reuse the milled up asphalt is the ability to maintain a constant
pavement elevation to keep bridge clearances and guardrail tolerances
in check. Without question the mill-and-fill technique for asphalt
pavement restoration is one of the great advantages of paving with
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